Submarines and aircraft dominate many naval friendly-fire cases

How common were naval friendly-fire incidents between 1900 and 1945?

They become numerous when submarine misidentification and friendly air attacks are included, while ship-on-ship cases are rarer.

The count depends on which kinds of incident are included. British submarines sometimes fired torpedoes at other British submarines after misidentification, and friendly aircraft also attacked submarines. Direct ship-on-ship friendly fire was less common, although it did occur. Measuring naval friendly fire only through surface-gun incidents between major warships misses much of the pattern.